Various types of sensors are being used to monitor personal physiological or biometric parameters related to health and/or performance during specified events or time periods, as well as during everyday activities. Monitoring of parameters such as heart rate, blood pressure, respiration rate, oxygen saturation, blood chemistry, blood flow, etc. under various environmental and use conditions presents numerous challenges in providing an acceptable sensor signal for processing. For example, motion artifacts generated by movement of the user and/or sensor during use may decrease accuracy of the resulting signal analysis results if not properly accommodated. Similarly, variation in positioning of the sensor relative to an expected placement, or movement during use may result in decreased accuracy. Changes in ambient conditions, such as variations in ambient light, sound, vibration, etc. may also contribute to noise in the sensor signal.
Biometric sensors have been integrated with earphones and headphones as the ear has been identified as being particularly amenable to photoplythysmography (PPG), or the optical volumetric measurement of blood flow, and similar optical measurements. Pulse oximetry sensors have been integrated into the cushion of circumaural headsets to measure blood oxygen saturation. Earphones, ear buds, headphones, and similar devices provide a convenient form factor that users are generally familiar with and comfortable with positioning of the devices.